1. Field of the Invention
The invention relates to ballistic resistant composites for use in airplanes and other vehicles, which meet particular structural, impact and ballistic requirements. More particularly, the invention pertains to composite structures incorporating high strength, ballistic resistant panels and aerospace grade honeycomb, which composite structures have superior structural, impact and ballistic performance at a light weight.
2. Description of the Related Art
Ballistic resistant articles containing high strength fibers that have excellent properties against projectiles are well known. High strength fibers conventionally used include polyolefin fibers, such as extended chain polyethylene fibers, and aramid fibers, such as para- and meta-aramid fibers. For many applications, the fibers may be used in a woven or knitted fabric. For other applications, the fibers may be encapsulated or embedded in a matrix material to form non-woven rigid or flexible fabrics.
Various ballistic resistant constructions are known that are useful for the formation of hard or soft armor articles such as helmets, structural panels and ballistic resistant vests. For example, U.S. Pat. Nos. 4,403,012, 4,457,985, 4,613,535, 4,623,574, 4,650,710, 4,737,402, 4,748,064, 5,552,208, 5,587,230, 6,642,159, 6,841,492, 6,846,758, all of which are incorporated herein by reference, describe ballistic resistant composites which include high strength fibers made from materials such as extended chain ultra-high molecular weight polyethylene. These composites display varying degrees of resistance to penetration by high speed impact from projectiles such as bullets, shells, shrapnel and the like.
Honeycomb materials are generally characterized by alternating single-walled and double-walled geometric cells, which enable the structure to be highly resilient and lightweight. More particularly, aerospace honeycomb is a honeycomb-shaped structural material that is commonly employed in composites forming structural members in aircraft, vehicles, as well in other articles such as sporting equipment and personal care products, because of their low weight, high strength and versatility. In recent years, such desirable properties have made honeycomb structures increasingly popular for use in composite structures together with ballistic resistant materials to a composite having excellent ballistic resistance in addition to shock-absorbing protection, together with superior structural properties.
Currently, there exists a growing demand for the enhancement of ballistic and forced entry resistant materials, particularly ballistic and forced entry resistant door and wall panels for use in commercial airlines and maritime vessels, to provide improved security and protection to vessel crew and enhance overall passenger safety. For example, U.S. Pat. No. 6,568,310 teaches a composite door including a woven ballistic resistant layer surrounded on each side by a mesh or mail material with a structural honeycomb being bonded to each mesh layer. U.S. Pat. No. 6,703,104 teaches a composite panel for use in aircraft interiors including a honeycomb core that is surrounded on each side by layers of fiberglass and having a woven fabric on the outermost surfaces of the fiberglass layers. U.S. Pat. No. 6,825,137 teaches a composite ballistic resistant panel for use as a structural member in an aircraft, which panel includes a honeycomb that is directly attached to a woven ballistic resistant material on one surface and to a fire resistant fibrous film on its other surface. U.S. Pat. No. 6,976,658 teaches a cockpit door formed by laminating a layer of an aromatic polyamide between a honeycomb on one side and a reinforcing member on its other side.
The present invention provides an alternate composite structure to those described in the related art. Particularly, the present invention provides a composite having non-woven fibrous layers juxtaposed with a central panel which comprises a honeycomb-shaped structure which comprises a plurality of closely packed geometric cells. One or more layers of a fire resistant material, such as fiberglass, may be attached to one or more surfaces of the non-woven fibrous layers to provide fire resistance. The composites of the invention have excellent structural properties while also meeting or exceeding the requirements of the National Institute for Justice level III-A ballistic penetration standard. Accordingly, they are particularly useful for the formation of structural members of airplanes and other vehicles, such as doors and bulk head structures.